W-54011 is a potent and orally active non-peptide C5a receptor antagonist. W-54011 inhibits the binding of 125I-labeled C5a to human neutrophils with a Ki value of 2.2 nM. W-54011 also inhibits C5a-induced intracellular Ca2+ mobilization, chemotaxis, and generation of ROS in human neutrophils with IC50s of 3.1 nM, 2.7 nM, and 1.6 nM, respectively.